The present invention relates generally to photoelectric imaging devices and, more particularly, to a photoelectric imaging device that is automatically adjustable in the field to compensate for mis-alignment which may occur in such devices.
Photoelectric imaging devices are used to produce machine-readable data which is representative of the image of an object, e.g. a page of printed text. As used herein, the phrase "photoelectric imaging device" means any device which generates data representative of an imaged object through use of a photosensor array such as a charge coupled device (CCD). Photoelectric imaging devices include devices such as camcorders and digital cameras which instantaneously focus an entire image which is to be captured onto a two dimensional photosensor array. Photoelectric imaging devices also include line-focus systems which image an object by sequentially focusing narrow "scan line" portions of the object onto a linear photosensor array by sweeping a scanning head over the object. Such devices, commonly referred to as optical scanners include computer input devices usually referred to simply as "scanners" as well as facsimile machines and digital copy machines.
In a line-focus system, a light beam from an illuminated line object is imaged by a lens on a linear photosensor array which is positioned remotely from the line object. The linear photosensor array is a single dimension array of photoelements which correspond to small area locations on the line object. These small area locations on the line object are commonly referred to as "picture elements" or "pixels." In response to light from its corresponding pixel location on the line object, each photosensor pixel element in the linear photosensor array (sometimes referred to simply as "pixels") produces a data signal which is representative of the light intensity that it experiences during an immediately preceding interval of time known as a sampling interval. All of the photoelement data signals are received and processed by an appropriate data processing system.
In a color optical scanner, a plurality of spectrally separated imaging beams (typically red, green and blue beams) must be projected onto photosensor arrays. Some color optical scanners employ beam splitter devices for spectrally separating an imaging light beam into color component beams. These separate color component beams are projected onto separate linear photosensor arrays. Other optical scanners project color component images on a single linear array in a series of separate scanning passes.
The construction and operation of color optical scanners employing beam splitter assemblies and photosensor arrays are fully disclosed in the following United States patents: U.S. Pat. No. 4,870,268 of Vincent et al. for COLOR COMBINER AND SEPARATOR AND IMPLEMENTATIONS; U.S. Pat. No. 4,926,041 of Boyd for OPTICAL SCANNER (and corresponding EPO patent application no. 90306876.5 filed Jun. 22, 1990); U.S. Pat. No. 5,019,703 of Boyd et al. for OPTICAL SCANNER WITH MIRROR MOUNTED OCCLUDING APERTURE OR FILTER (and corresponding EPO patent application no. 90312893.2 filed Nov. 27,1990); U.S. Pat. No. 5,032,004 of Steinle for BEAM SPLITTER APPARATUS WITH ADJUSTABLE IMAGE FOCUS AND REGISTRATION (and corresponding EPO patent application no. 91304185.1 filed May 9, 1991); U.S. Pat. No. 5,044,727 of Steinle for BEAM SPLITTER/COMBINER APPARATUS (and corresponding EPO patent application no. 91303860.3 filed Apr. 29, 1991); U.S. Pat. No. 5,040,872 of Steinle for BEAM SPLITTER/COMBINER WITH PATH LENGTH COMPENSATOR (and corresponding EPO patent application no. 90124279.2 filed Dec. 14, 1990 which has been abandoned); U.S. Pat. No. 5,227,620 of Elder, Jr. et al. for APPARATUS FOR ASSEMBLING COMPONENTS OF COLOR OPTICAL SCANNERS (and corresponding EPO patent application no. 91304403.8 file May 16, 1991); and U.S. Pat. No. 5,410,347 of Steinle et al. for COLOR OPTICAL SCANNER WITH IMAGE REGISTRATION HOLDING ASSEMBLY, which are all hereby specifically incorporated by reference for all that is disclosed therein.
In imaging devices and particularly the line-focus system described above, it is imperative for accurate imaging that the light beam from the object be accurately aligned with the photosensor array. In a typical line focus scanning device, before reaching the photosensor array, the imaging light beam is transmitted and/or reflected by several optical components. Even a slight mis-alignment of any of these optical components can cause a serious mis-alignment between the beam and the photosensor array and result in a corresponding degradation in scanning quality. Although the various optical components are precisely aligned upon manufacture of the scanning device, factors such as physical shock and temperature and humidity variations experienced in the field can lead to instability in adhesives and other mechanical parts of the scanning device, thus leading to misalignment.